The present invention relates to an attitude control device for in-space propellant depot that controls an attitude angle of an in-space propellant depot while suppressing a disturbance torque such as the one due to solar radiation pressure.
In-space propellant depots are generally represented as a nonlinear time varying system with nonlinearlity of its mechanical structure and time-varying inertial moment due to sloshing of propellant, and exhibit subharmonic resonance, superharmonic resonance and parametric resonance together with primary resonance when exposed to the disturbance torque containing a frequency near a resonance frequency of the in-space propellant depots.
U.S. Pat. No. 7,957,854 B2 discloses an active vibration damping system for precision pointing spacecraft that identifies a plurality of system parameters in a transfer function of a spacecraft characterizing dynamics thereof applying a known excitation signal, and generates a control torque for suppressing a vibration of the spacecraft using a reaction wheel based on the plurality of system parameters identified.
The prior art in U.S. Pat. No. 7,957,854 B2, if applied to an in-space propellant depot as in U.S. Pat. No. 7,575,200 B2, introduces undesirable vibration of frequencies near resonance frequencies other than primary resonance frequencies of the in-space propellant depot, and thus fails to suppress effectively the vibration induced by the disturbance torque as a result of its negligence of a plurality of types of resonance causing the vibration.